The Minneapolis Chain of Lakes by bicycle: Glacial history, human modifications, and paleolimnology of an urban natural environment

The Minneapolis Chain of Lakes is a focal point of natural beauty in the heart of the city. Given the recreational and aesthetic imperative, these urban waterbodies have for decades been heavily managed for water quality and lake level. In the early stages of development of Minneapolis' civic infrastructure, the area's lakes and streams, as well as the Mississippi River, were given special consideration for preservation. This did not, however, mean that the lakes were preserved in their "natural" state, for they were connected by channels, dredged and filled to turn wetlands into open water and dry land, and even reshaped to better conform to the prevailing fashion of design. These manipulations had dramatic effects on the Chain's smallest lake, Brownie, which became meromictic after a rapid drop in lake level caused by ditching across the divide to Cedar Lake. The lakes and surrounding area were important sources of subsistence for Dakota and Ojibwe people through the middle of the nineteenth century, and some of the earliest substantive interactions between missionaries and Native Americans in Minnesota played out around the Chain of Lakes and nearby Mississippi River valley. The relative orientation of the lakes (and of other groups of lakes in the Twin Cities), and some lakes' unusual depths relative to surface areas, result from their formation by melting of ice blocks buried in valley train fill during final retreat of the Laurentide ice sheet. Below tens to hundreds of feet of glacial material, mapping of bedrock surfaces indicates the presence of paleo- Mississippi River channels dating from at least two previous interglacials. The integration of multiple subdisciplines of geology and of various basic sciences within paleolimnology and limnogeology, as well as the relevance to students of historical and environmental information, makes lake sediment studies well suited to handson, place-based educational approaches as stand-alone courses or laboratories for a number of different core curriculum and nonmajor classes.